The invention relates to a belt retractor for a vehicle safety belt. The belt retractor comprises a frame, a belt spool rotatably mounted in the frame, a locking mechanism which is provided with a release disk and by means of which the belt spool can be blocked against rotation in the frame, and a control disk as well as a reduction gear that couples the belt spool with the control disk.
A belt retractor of that kind is known from German Utility Model 298 20 086. The control disk serves for operating a so-called child protection. When the child protection is activated, the belt webbing can no longer be drawn off the belt retractor, but only rolled up. This makes it possible to solidly connect a child""s safety seat with the vehicle. In order to activate the child protection function, the belt webbing is drawn off the belt spool almost completely. The child protection is automatically deactivated when the belt webbing is again rolled up on the belt spool almost completely.
There have been recent attempts to integrate further functions in the belt retractor. Special attention is paid to the possibility of performing a so-called occupant sensing, i.e. obtaining information on whether or not the vehicle seat associated with the belt retractor is occupied. This may be done by sensing whether or not the safety belt is used. It is presupposed here that a vehicle occupant does use the corresponding safety belt. When it is determined that a vehicle occupant is present, various safety systems like a belt tensioner may be cleared. When the safety belt is not used, the belt tensioner is deactivated in a vehicle accident as there are no advantages to be got from an unused belt being tensioned.
It is the object of the invention to further develop a belt retractor of the kind initially mentioned to the effect that both a child protection function and an occupant sensing may be realized at low expenditure.
This is achieved in a belt retractor which comprises a frame, a belt spool rotatably mounted in the frame, and a locking mechanism which is provided with a release disk and by means of which the belt spool can be blocked against rotation in the frame. The belt retractor further comprises a control disk as well as a reduction gear that couples the belt spool with the control disk. A rocking lever is provided which is adapted to be pivoted by the control disk between a release position in which it does not cooperate with the release disk, and a blocking position in which it engages in the release disk, whereby the belt spool can be blocked against rotation. A switch is provided which is adapted to be actuated by the control disk when a predetermined amount of belt webbing has been drawn off the belt spool and the control disk has been turned into a predetermined position. Thus, the belt retractor proposed combines the two functions child protection and occupant sensing in that a single control disk both switches the rocking lever, by means of which the child protection function may be realized, and directly or indirectly actuates the switch by means of which it can be sensed whether the belt webbing has been drawn off the belt retractor, which indirectly indicates that a vehicle occupant is present.
Preferably, the switch is a microswitch with a contact element able to be actuated by a ramp surface on the control disk. This results in minimum construction expenditure since the microswitch just needs to be attached to the belt retractor such that it is immediately actuated by the control disk.
Preferably, the rocking lever cooperates with a dead-center spring such that the blocking position and the release position are situated on the one and the other side of the dead center, respectively. In this manner, there is provided a bistable rocking lever which is adapted to be easily switched to and fro between the one and the other position by the control disk. For the purpose, two stops on the control disk may preferably be used, which are adapted to cooperate with the rocking lever. Especially low construction expenditure results when a spring shackle being integrally formed on the rocking lever is used for realizing the dead-center spring.
According to a preferred embodiment of the invention, there is provided a reversible switch which is adapted to sense the switching state of the rocking lever. This makes it possible to electronically interrogate the status of the belt retractor in respect of the child protection function. For example, a gas bag may be deactivated in this manner when a child safety seat is attached on the vehicle front seat by means of the belt retractor.
The reversible switch may for instance be disposed such that its contact element is directly actuated by the rocking lever when the latter is in the position for the child protection function, for instance. As an alternative, it may be provided that the rocking lever is actuated indirectly, for instance by a drag disk which is coupled with the control disk and comprises a ramp surface which is adapted to cooperate with the contact element of the rocking lever. This drag disk comprises a gate in which a spigot mounted on the control disk engages, so that the control disk entrains the drag disk whenever the spigot abuts at one end of the cam. Since the rocking lever is actuated indirectly, it is possible to mount it at a suitable location on the belt retractor remote from the rocking lever.
Advantageous configurations of the invention may be taken from the subclaims.